The invention relates to a luminaire comprising:
a housing with means for accommodating an electric lamp therein; PA1 a mounting bracket for fastening to a support; PA1 a coupling which connects the housing adjustably to the mounting bracket. PA1 the first and the second part being rotatable relative to one another, and PA1 the coupling having a blocking device with an operational position from which it can be released, and with release positions, PA1 which blocking device in its operational position locks the first and the second part in a previously defined mutual rotational position.
Such a luminaire is known from U.S. Pat. No. 5,353,211. In the known luminaire, the coupling consists of a threaded bolt which is screwed into a threaded hole in the housing. Before the threaded bolt is completely tightened, the bolt forms a horizontal shaft about which the housing can be pivoted upwards or downwards so as to illuminate the desired field by means of the luminaire. Once the correct position of the housing has been found, the latter is fixed in that the bolt is tightened.
Luminaires are often used in locations where they are accessible with difficulty, often from one side only, for example from the rear. This is the case, for example, when a luminaire is used for lighting, for example, a sports ground and is mounted against a framework at the top of a mast or at the edge of a roof, for example the edge of the roof of a spectator stand. It may be necessary in that case to loose the coupling and rotate the housing in the case of maintenance of the luminaire, for example for cleaning a reflector in the luminaire or a transparent plate which closes off the housing, or for replacing a lamp.
In a luminaire of the known kind, the housing must be accurately realigned when the maintenance work has been completed so as to achieve the original adjustment again. This is time-consuming and requires craftsmanship. The necessity of a repeated alignment is accordingly a major disadvantage of the known luminaire.
The adjustment of the housing with respect to the mounting bracket, with the object of throwing the light beam formed by the luminaire in the desired direction, should not be confused with the positioning of an electric lamp in the housing of the luminaire so as to give this lamp the correct position relative to a reflector in the housing and to create a light beam of the desired shape, i.e. with the desired light distribution. The essence of the luminaire described in the cited U.S. Pat No. 5,353,211 indeed lies in this adjustment of the shape of the light beam.